Nearly Zero-Energy Buildings (nZEB) and Their Effect on Social Housing in Ireland: A Case Study Review

Nearly zero-energy buildings (nZEB) are a relatively new concept, and they are buildings designed with a very high energy performance. Current EU Directives legislate that all new public buildings are nZEB compliant by 2021, where new buildings are expected to use up to three times less energy than current buildings, and ultimately impact on costs involved. This potentially has huge implications for social housing developments, particularly in Ireland, where social housing is a key area of construction, accounting for 10% of all Irish households. Therefore, the aim of this study is to undertake research on social housing in Ireland, and by identifying whether it can be nZEB compliant, factoring design, materials usage, construction techniques, labour approaches and appropriate cost-cutting methods. To assist with the research, a mixed methods approach is adopted, combining a literature review, three case studies, semi-structured interviews, focus group and questionnaire survey, with experienced construction professionals in the Irish construction industry. The resultant data is organised in a tabulated format, with components from each case study listed and discussed, identifying their similarities and differences. Cost comparisons are undertaken to illustrate cost differences between each case study and establishing if nZEB benefit or hinder the costs associated when constructing social housing. From analysing the results, extra costs are evident for social housing nZEB buildings in areas including higher performing windows, increased insulation in walls and attics, heat recovery ventilation and airtight attic hatches. Cost savings can be made by not having a chimney stack, and the elimination of a traditional heating system, amongst others. Overall, the key contribution of this research identifies that new nZEB buildings have many advantages and disadvantages; nevertheless, in the short term, they are more expensive to construct but, in the long term, have potential financial savings for new social housing construction projects in Ireland.